Platinum and its alloys are widely used in the manufacture of ovens for the glass industry and for crucibles, e.g., nozzles, in the production of glass and mineral fibers (strands) because of their corrosion resistance and mechanical strength.
Generally, these alloys consist of platinum with 5, 10 or 20% by weight rhodium added. Other alloys consist of platinum, palladium and rhodium, e.g., containing more than 30 to less than 89% of platinum, more than 1 to less than 25% rhodium and more than 10 to less than 69% palladium (British Patent No. 1,421,141). Still others comprise 10-30% rhodium or iridium and for 30 to 50% platinum, the remainder being palladium, German OL 1,950,468.
German Patent 1,194,585 which corresponds to British specification 1,064,474 discloses alloys containing in addition to platinum, palladium and rhodium up to 2% of noble metals (by weight).
Platinum alloys containing gold as an alloying element have been suggested as material which is resistant to molten glass. German OL No. 1,533,224 discloses alloys containing 60-97% of platinum, 2 to 25% of rhodium, and 1 to 10% of gold by weight; British Patent No. 1,242,921 discloses alloys containing a minimum of 60% of platinum, 2 to 25% of rhodium, 0 to 20% of iridium, 2 to 10% of gold, 0 to 5% of copper, and 0-10% of palladium.
It is an object of the present invention to provide alloys of platinum, palladium, rhodium and gold which are resistant to molten glass, particularly those containing silicates, and have properties superior to those presently known relative to their use as construction materials for glass processing apparatus.